Many types of credentials include one or more human-discernable, optical security features on a laminated structure. If a nefarious individual obtains credential blanks, he may attempt unauthorized personalization of the credential by adding security features that appear authentic. Adding security features by printing, or the like, can often be performed with relatively inexpensive and ubiquitous technologies, and/or with little specialized knowledge or skill. Some credentials coat a substrate with an opaque coating, and add one or more security features by selectively causing certain regions of the opaque coating to become fully or partially transparent to the substrate below (e.g., by ablation or some other process). If the substrate and coating are of contrasting colors, such a process can be used to form a two-color (e.g., half-tone) personalization image (e.g., of the credential holder's face). Adding security features by ablation of a coating, or the like, can often involve be more difficult that simply printing or embossing a security feature. However, many such processes can still be relatively simple to spoof (e.g., to personalize the credential in a manner that is good enough to pass visual inspection, etc.) without specialized knowledge, skill, equipment, etc.